Medium density fibre board, particle board, and other panel boards, plywood and veneers and similar engineered wood products are typically composed of lignocellulosic or cellulosic material of small dimension—whether as particles or sheets—combined with an adhesive or resin with the composition subsequently pressed or shaped into a panel or similar and heated to cure the adhesive to fix the shape and provide internal bonding.
In industry, the adhesives that are most commonly used are urea-formaldehyde (UF) resins and phenol-formaldehyde resins. Isocyanate resins are also used. Phenolic resins provide composite materials with superior material properties including stability, hardness and water resistance. UF resins provide good strength and are extremely cost competitive. But both resins have disadvantages. Both are synthetic resins derived from fossil fuels and both result in the formation and emission of volatile organic compounds, particularly formaldehyde, during both the manufacture and use of the resulting panels.
A resin that retains the material properties of UF and phenolic resins but is formaldehyde free and made from renewable or mostly renewable resources would potentially be of benefit to the wood composite industry, wood composite users, indoor living spaces and the environment. Ideally any such resin would be compatible with current production facilities and schedules particularly in regard to such matters as resin handling and application, pressing and curing. Ideally, it would also able to be formulated using typical adhesive manufacturing practice.
It is an object of the invention to provide an adhesive suitable for adhering wood and other lignocellulosic substrates that is preferably formaldehyde free or can be used to reduce formaldehyde emissions, and comprised substantially of renewable materials, or to at least provide the public with a useful choice.